Metal phthalocyanine intermediates for the preparation of polymers

ABSTRACT

Metal 4, 4&#39;, 4&#34;, 4&#34;&#39;-tetracarboxylic phthalocyanines (MPTC) are prepared by reaction of trimellitic anhydride, a salt or hydroxide of the desired metal (or the metal in powdered form), urea and a catalyst. A purer form of MPTC is prepared than heretofore. These tetracarboxylic acids are then polymerized by heat to sheet polymers which have superior heat and oxidation resistance. The metal is preferably a divalent metal having an atomic radius close to 1.35Å.

ORIGIN OF THE INVENTION

The invention described herein was made in the performance of work undera NASA contract and is subject to the provisions of Section 305 of theNational Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat.435; 42 U.S.C. 2457).

This is a division of application Ser. No. 415,880 filed Sept. 8, 1982,now U.S. Pat. No. 4,456,268, granted May 22, 1984.

FIELD OF THE INVENTION

This invention relates to metal phthalocyanine tetracarboxylic acids, toa novel method of synthesizing the same and to polymers of the same.

BACKGROUND OF THE INVENTION

In recent years there has been an increasing demand in industry anddefense for polymeric substances which would either remain intact orcontinue to serve in a more or less degraded state under conditionswhere temperatures far above the ordinary are encountered. In many caseshighly cross-linked organic polymers have been found promising. Thephthalocyanine structure is one of the most thermally stable organicstructures known. Attractive properties like resistance to chemicalattack, electrical properties, catalytic activity and moderate cost ofmanufacture with good coloring properties have made phthalocyanines theobject of intensive world-wide investigations. Many attempts tosynthesize polymers based on phthalocyanines have failed to provide theexpected thermal stability. Phthalocyanine polymers so far produced haveshown less thermal stability than the phthalocyanine monomer itselfbecause of the presence of impurities, weak chemical bonds and lowdegree of polymerization with structural inhomogeneity. Impurities havethe considerable effect of decreasing thermal stability of thephthalocyanine monomers as well as the polymers produced from them. Itis well known that the way in which the repeating units are linked isreflected in the properties of the polymers. If the repeatingphthalocyanine mer units are linked in the way phenyl groups are linkedin biphenyl, the conjugation extends throughout the macromoleculethereby increasing the extent of delocalization of the π-electrons. Thisis expected to increase the conductivity as well as the thermalstability of the phthalocyanine polymers.

OBJECTS OF THE INVENTION

Objects of the invention include methods of preparing metalphthalocyanine monomers in a pure state and the preparation from suchmonomers of thermally stable sheet polymers which have biphenyl typelinkages between the mer units, high thermal and thermal oxidativestability and electrical conductivity, also good flame and fireresistance.

BRIEF DESCRIPTION OF THE INVENTION

A metal phthalocyanine tetracarboxylic acid (MPTC) is prepared in pureform by reaction of trimellitic anhydride with urea and a soluble metalsalt in the presence of a suitable catalyst and in a suitable solvent.The metal is that which it is desired to introduce into the intendedmetal complex. The resulting MPTC, after separation and purification, ispolymerized by heat in a vacuum or in an atmosphere of an inert gas suchas nitrogen. The MPTC prepared by this method is purer than MPTC'sprepared heretofore and the polymer derived from it is free ofimpurities which detract from its useful properties.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural formula of the metal 4,4',4",4'"-tetracarboxyphthalocyanine which is to be polymerized.

FIG. 2 is a structural formula of the resulting polymer.

FIG. 3 is a graph showing TGA and DTG curves for these polymers,including the polymer of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION EXAMPLE 1 Preparation of Copper(II) phthalocyanine tetracarboxylic acid 1

This compound has the formula ##STR1## wherein M is copper (II).

It was prepared as follows: 12.0 g Copper (II) sulfate pentahydrate,33.8 g trimellitic anhydride, 4.5 g ammonium chloride, 0.5 g ammoniummolybdate and 60 g urea were finely ground together and placed in a 500ml three-necked flask containing 25 ml of nitrobenzene. The flask wasprovided with a thermometer, condenser and a mechanical stirrer. Thetemperature of the flask was slowly increased to 180° C. and maintainedat 185° C. for four hours. The color of the reaction mixture graduallydeepened and finally a deep colored solid was obtained. The product wasground well and washed with methanol until it was free fromnitrobenzene. The solid product was added to 500 ml of 1.0N hydrochloricacid saturated with sodium chloride, boiled briefly, cooled to roomtemperature and filtered. The resulting solid material was treated with500 ml of 2.0N sodium hydroxide containing 200 g sodium chloride andheated at 90° C. until the evolution of ammonia ceased. The solutionafter filtration was treated with 500 ml 2.0N hydrochloric acid and theproduct was separated by centrifugation. The residue was redissolved in0.1N sodium hydroxide and filtered to separate the insoluble materials.The compound was re-precipitated with 1.0N hydrochloric acid andcentrifuged to obtain the solid material. Dissolution and precipitationsteps were repeated twice. Then the compound was washed until chloridefree and finally washed with methanol. The blue product was dried at 100° in vacuum.

Compound C₃₆ H₁₆ N₈ O₈ Cu, (CuPTC): Calcd: C, 57.5; H, 2.14; N, 14.9;Cu, 8.45; Eq. wt. 188.0. Found: C, 57.1; H, 2.3; N, 15.0; Cu, 8.5; Eq.wt. 187.6. IR absorption bands (cm⁻¹): 3500-2500 (broad), 1691 (broad),1614m, 1578m, 1508m, 1329m, 1279m, 1246m (broad), 1188m, 1149m, 1089s,1050w, 968w, 940w, 851w, 783w, 774w, 736s.

EXAMPLES 2 AND 3

The cobalt and nickel analogues of 1 were prepared by the same methodusing in Example 2 cobalt sulfate and in Example 3 nickel sulfate. Theempirical formulae and analytical results obtained were as follows:

Example 2 (Cobalt)

Compound C₃₆ H₁₆ N₈ O₈ Co, (CoPTC): Calcd: C, 57.8; H, 2.15; N, 15.0;Co, 7.88; Eq. wt. 186.9. Found: C, 57.5; H, 2.2; N, 15.2; Co, 7.90; Eq.wt. 186.7. IR absorption bands (cm⁻¹): 3500-2500 (broad), 1696 (broad),1613m, 1586m, 1521m, 1330m, 1281m, 1246m, (broad), 1189m, 1149m, 1090s,1050w, 9730w, 944w, 848w, 782w, 773w, 742s.

Example 3 (Nickel)

Compound C₃₆ H₁₆ N₈ O₈ Ni, (NiPTC): Calcd: C, 57.86; H, 2.15; N, 15.0;Ni, 7.86; Eq. wt. 186.8. Found: C, 57.91; H, 2.2; N, 15.05; Ni, 7.88;Eq. wt. 186.6. IR absorption bands (cm⁻¹) 3500-2500 (broad), 1699(broad), 1615m, 1590m, 1530m, 1333m, 1274m, 1238m (broad), 1189m, 1150m,1089s, 1050w, 976w, 944w, 848w, 779w, 738s.

Any mono-, di- or higher valency metal M may be used in place ofdivalent copper, cobalt and nickel, e.g., Cu(I), cobalt and nickel inother valence states, Fe(II), Fe(III), Zn,Al, lead, tin, palladium,germanium, vanadium, platinum and molybdenum in various valence states;monovalent metals such as Li, Na and K, etc. Where the metal ismonovalent two atoms will be present, one atom above and the other atombelow the plane of the phthalocyanine molecule. With a trivalent metalsuch as aluminum, one of the valences may be satisfied by a ligand suchas Cl, F, acetate, etc., e.g., the metallic compound can be representedas M' where M' is the metal atom and X is an inorganic atom or radicalor an organic group.

Preferably the metal is divalent and has an atomic radius close to 1.35Å. Metals of substantially larger atomic radius may not fit well intothe molecule and metals having a substantially smaller atomic radius aremore likely to be extracted by strong acids, e.g., concentrated sulfuricacid. Metals having ligands may be susceptible to hydrolytic action.

Any soluble salt or hydroxide of the selected metal may be used providedthe counter ion is compatible with the reactants and the reactionproduct. For example, the metal M may be used in the form of itssulfate, chloride, nitrate, acetate, oxalate, etc. Also, it may be usedin the form of a finely divided metallic powder. Preferably thereactants are used in approximately stoichiometric proportions. Thereactants are trimellitic anhydride ##STR2## (which provides thebenzenoid rings), urea and possibly also the ammonium chloride. Theammonium chloride may be used alone as the catalyst but the use ofammonium molybdate as well allows the reaction to proceed at a lowertemperature and increases the yield.

Nitrobenzene is an advantageous solvent because, besides beingunreactive and being a good solvent for the reactants, it has a highboiling point (210° C.). Other aprotic solvents such as quinoline andtetralin may be used. Yields of 90% or more are obtainable.

The metal M may be removed from the molecule as by dissolving it inconcentrated sulfuric acid to produce the hydrogen (protonated) speciesin which each of the two covalent bonds is connected to hydrogen. Theprotonated species may then be treated with an alcoholic solution of ametal salt, e.g., copper sulfate, to insert the metal, e.g., Cu(II). Inthis way one metal may be substituted for another. However, it ispreferred to choose the desired metal initially and to insert it in thephthalocyanine molecule in the synthesis of the tetracarboxylic acid.

EXAMPLE 4 Polymerization of MPTC--Method 1

About 1-2 g of metal phthalocyanine tetracarboxylic acid was finelyground in a small vibrating ball mill and placed in a polymerizationtube. The tube was connected to an apparatus provided with a tube tocondense volatile products, stopcocks to connect gas collection tube andIR cell for gaseous analysis. The apparatus was connected to vacuumsystem. Reaction tube was carefully evacuated to 10⁻⁵ -10⁻⁶ torrpressure and heated to 450° C. The gaseous and volatile products werecondensed in separate traps using liquid nitrogen. The reaction wasfound to be completed after one hour of heating at 450° C. in vacuum.

EXAMPLE 5 Polymerization of MPTC--Method 2

Finely ground metal phthalocyanine tetracarboxylic acid was taken in areaction tube fitted with a glass enclosed iron-constantan thermocoupleand inlet and outlet tubes. The polymerization tube was carefully purgedwith nitrogen by repeated evacuation and refilling. Then it wasgradually heated to 450° C. in a current of nitrogen and maintainedtemperature of 450°-500° C. in a current of nitrogen for one hour.

Methods 1 and 2 were applied to produce the divalent copper, cobalt andnickel compounds. Analytical results were the same for products of thetwo methods and were as follows:

(1) Compound C₃₂ H₁₂ N₈ Cu: Calcd: C, 67.18; H, 2.11; N, 19.58; Cu,11.2. Found: C, 66.9; H, 2.21; N, 19.8; Cu, 11.5. IR absorption bands(cm⁻¹): 1610w, 1503w, 1407w, 1328m, 1271m, 1164m, 1118w, 1089m, 1065m,898w, 773w, 754w, 738s.

(2) Compound C₃₂ H₁₂ N₈ Co: Calcd: C, 67.73; H, 2.13; N, 19.75; Co,10.39. Found: C, 67.6; H, 2.3; N, 19.95; Co, 10.46. IR absorptlon bands(cm⁻¹): 1599w, 1502w, 1408w, 1329m, 1292m, 1115w, 1090m, 1060w, 940w,902w, 785w, 740w, 741s.

(3) Compound C₃₂ H₁₂ N₈ Ni: Calcd: C, 67.76; H, 2.13; N, 19.75; Ni,10.35. Found: C, 67.8; H, 2.18; N, 19.92; Ni, 10.43. IR absorption bands(cm⁻¹): 1602w, 1519w, 1409w, 1334m, 1287m, 1157m, 1115w, 1086m, 1053w,944w, 914w, 782w, 745w, 743m.

The polymerization reaction proceeds by way of the elimination ofcarboxyl groups and the formation of a sheet polymer in which the merunits are linked by biphenyl linkage. The formula of the polymer may beexpressed as follows: ##STR3##

These polymers are soluble in concentrated (98%) sulfuric acid,concentrated (36%) hydrochloric acid, chlorosulfuric acid and trimethylsulfonic acid. They have high thermal resistance and have a higherelectrical conductivity (as well as a higher thermal oxidativeresistance) than the phthalocyanine monomers. Threshold temperatures atwhich major decomposition occurs are typically higher than 450° C. inair; they have a high char yield in nitrogen and in nitrogen atmosphereno catastrophic decomposition has been observed up to 1000° C. Charyields at 800° C. in nitrogen and electric conductivities are given inTable I.

                  TABLE 1                                                         ______________________________________                                                            CHAR     CONDUCTIVITY                                                         YIELD    (22-300° C.)                              POLYMER  PDT.sub.max °C.                                                                   (800° C.)                                                                       (Ω-cm)                                     ______________________________________                                        CuPc-Sheet                                                                             760        90.5%    3.2 × 10.sup.-10 -3.8                                                   × 10.sup.-5                                Polymer                                                                       CoPC-Sheet                                                                             860        89.0%    1.8 × 10.sup.-8 -2.3                                                    × 10.sup.-3                                Polymer                                                                       NiPc-Sheet                                                                             890        93.0%    1.4 × 10.sup.-8 -3.9                                                    × 10.sup.-5                                Polymer                                                                       ______________________________________                                    

In FIG. 3 of the drawing the results plotted are for Cu, Co and Ni sheetpolymers heated in an atmosphere of nitrogen. The ordinate scale on theleft represents percent decomposition and the ordinate scale on theright represents rate of weight loss. As will be seen the polymers didnot undergo substantial decomposition below 750° C. to 800° C. (Seecurves at top.) The rate of decomposition (lower set of curves) did notbecome substantial until about 750° to 900° C.

It will be apparent that purer metal phthalocyanine tetracarboxylicacids are provided, that a new and useful method of preparing them hasbeen provided and that new and useful polymers and methods of producingthem have been provided.

It is claimed:
 1. A method of preparing an isolated metal4,4',4",4"'-tetracarboxylic phthalocyanine which comprisesa. heating atabout 185° C. for about four hours a reaction mixture comprising ananhydride consisting essentially of trimellitic anhydride, a source ofmetal selected from finely divided powders and salts of said metal, andurea in the presence of a catalyst comprising ammonium chloride andammonium molybdate in a nitrobenzene reaction medium, and b. recoveringthe desired metal 4,4',4",4"'-tetracarboxylic phthalocyanine from thereaction mixture by,b.1. washing the reaction mixture with methanol togive a washed product, b.2. boiling the washed product in aqueousmineral acid to give an acid-wash product, b.3. treating the acid washproduct with inorganic hydroxide at elevated temperature until ammoniaevolution ceases and a soluble product results, b.4. precipitating thedesired metal 4,4',4",4"'-tetracarboxylic phthalocyanine as a solid fromthe soluble product, and b.5. isolating and washing the solid metal4,4',4",4"'-tetracarboxylic phthalocyanine with methanol and drying. 2.The method of claim 1 wherein the metal is a divalent metal having anatomic radius of approximately 1.35 Å.
 3. The method of claim 2 whereinthe metal is copper and the source of metal is a copper salt.
 4. Themethod of claim 2 wherein the metal is nickel and the source of metal isa nickel salt.
 5. The method of claim 2 wherein the metal is cobalt andthe source of metal is a cobalt salt.